Method and device for drilling precision holes



April 17, 1962 M. A. FRANK, sR

METHOD AND DEVICE FOR DRILLING PRECISION HOLES Filed March 23, 1959 R m m w.

Milton A. Frank 5::

ATTORNEY 3,029,664 METHOD AND DEVICE FOR DRILLING PRECISIUN HOLES Milton A. Frank, S12, 508 N. Market St., Frederick, Md. Filed Mar. 23, 1959, Ser. No. 801,419 9 Claims (Cl. 77-323) (Granted under Title 35, US. *Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to a method and apparatus for drilling small holes in metals.

There are drill assemblies on the market today which i will drill small holes in metals, but they are cumbersome,

expensive and extremey slow in operation. Many of these devices require special types of drills which are very costly compared to standard twist drills. A great deal of care is required in operating these drill assemblies because of the tendency of the drills to bend and break when excess pressure is brought to bear upon them.

It is the object of my invention to overcome these deficiencies. For example, my method and apparatus can be adapted to almost any type of drilling device at a very small cost. The apparatus is uncomplicated in design and simple in operation. It drills perfect small holes in the range of 0.0025 inches in diameter with standard types of drills, and at a faster rate than any other device now known on the market.

Other and more specific objects of my invention will become apparent upon a careful consideration of the following detailed description when taken together with the accompanying drawing in which:

FIG. 1 is a side perspective view of a standard jewelers drill assembly with my lever operated invention attached to the tailstock section, and with the drill bit being held stationary while the subject material is rotated.

FIG. 2 is a side view' of a modified tailstock section having my solenoid operated invention attached thereto, and designed so that the drill is rotated and the subject material is held stationary.

FIG. 3 is a perspective view along lines 3--3 of FIG. 1.

FIG. 4 shows the pawl and pawl holder assembly.

FIG. 5 is a sectional view along lines 55 of FIG. 4.

FIG. 6 is a sectional view along lines 6-6 of FIG. 4, showing the friction plunger mounting.

In drilling operations, standard drills of larger diameters have little tendency to bend or break because they have a small length-to-diameter ratio, which for example may range from 6-1 to about 20-1. Drills with smaller diameters but of the same length, however, have a much greater ratio; for example, a 0.025 in. diameter drill may have a length to diameter ratio of 80 to 1. As is well known, the greater the length to diameter ratio, the greater is the tendency of the drill to bend when pressure is applied to it. Of course this pressure can be greatly decreased, but only atthe expense of an increase in drilling time. I have developed a method and apparatus by taking all of these aspects into consideration.

My method consists of (l) causing a non-rotating drill to impinge repeatedly against and into the rapidly rotating object to be drilled, or (2) causing a rotating drill to impinge upon and into a stationary object to be drilled. The drill is reciprocated back and forth very rapidly Within the hole that is being drilled; or preferably, the drill is reciprocated as before, and in addition it is completely removed from the hole on each of its reversing strokes so that all of the chips may be removed at each stroke, thereby keeping the hole in a cleaned condition at all times. The amount of pressure applied as the drill means of a collet or chuck 18. The headstock of FIGJ ice strikes the bottom of the hole is controlled by limiting the depth by which the drill can pierce anobject each time the drill reciprocates. The maximum desirable increment of depth is determined by taking into consideration the size of the drill and the hardness of material being drilled. In the drilling of many metals this incremental forward advance of the drill was found to be best when limited to a range of from 1% to 10% of the drill diameter. However, since this incremental distance of depth depends to a great extent upon the resistance to cutting or hardness of the object being drilled, it should be understood that the outer limits of this range may have to be varied. This depth can easily be determined by trying various incremental depths to determine the maximum distance which the drill will impinge without bending or breaking.

The maximum reciprocating speed of the drill is only limited by the fatigue and strength limitations of the materials involved. My solenoid operated device as shown in FIG. 2 can, of course, reciprocate at a much faster rate than my manually operated device as shown in FIG. 1.

An example of my novel method will now be given which will show the conditions and the results of a certain drilling operation using the device as shown in FIG. 1. A hole of 0.005 inch in diameter was drilled through a inch piece of non-machined stainless steel (which had a diameter of /s) in approximately 15 minutes. A standard size drill was used; and the incremental depth was set at about 2 microns. The drill was brought up to touch the object to be drilled, in order to position said drill so that on the next stroke (first stroke of the drilling operation) the drill will advance up to the object and will then continue into the object a distance of 2 microns. Each stroke of the drill increased the depth of the hole by an additional 2 microns. The non-rotating drill was reciprocated in and out of the hole while the unmachined stainless steel object was rotated at about 3500 r.p.m. After the drilling Was completed the hole was examined through a microscope and it was found that there were no scratches or other irregularities.

As far as it is known, no other drilling machine can drill a hole of this depth, size and quality through a piece of non-machined stainless steel. A hole of this size could possibly be made by burring, but this would take a considerable amountof time and effort, and the hole would undoubtedly have many imperfections. I have drilled holes with the same degree of perfection in other meals, such as aluminum and platinum.

My novel apparatus will now be explained in detail. FIG. 1 discloses an entire jewelers drill 10 having a headstock section 12 and a tailtock section 14. The headstock 12, which does not form a part of my invention, can be any standard type of headstock which will hold and rotate a metallic object 16, said object being held by 2 (not shown) does not need to rotate the object tobe drilled because here the drill is rotated.

I have modified a standard tailstock 14 by the addition of my inventive features. As seen in FIGS. 1 and 2, the collet or chuck 20 holds the drill 22. A reciprocatable drill spindle or shank 24 extends through the stationary part of the tailstock section. The lock 25 is standard equipment. The micrometer 26, which is also standard on jewelers drills, is used for setting the incremental depth measurements, that is the distance that the drill or bit will penetrate an object to be drilled. These incremental distances or depth settings are obtained automatically by moving the ratchet wheel 28 by the desired number of notches 30, which in turn changes the micrometer setting and thereby repositions the spindle and the drill. This ratchet wheel is detachably attached to aoaaeea the micrometer so that other ratchet wheels having differently spaced notches can be employed. The ratchet wheel is turned by pushing the lever assembly 32 forward. Since the lever assembly 32 is connected to the spindle 24 by means of pin 34, the spindle, drill, and the pawl holder assembly 36 are also pushed forward, causing the pawl 38 to engage and move the ratchet wheel, and the drill to impinge against and into the object to be drilled. The lever assembly is then pushed rearward to complete the cycle.

A solenoid mechanism 40 in conjunction with a spring 42 as shown in FIG. 2 can be used in lieu of the manually operated lever system so that the operation can be performed automatically. The solenoid is electrically activated, and pushes the spindle, pawl holder assembly and drill forward at which time the solenoid is deactivated, whereupon the compressed spring 42 pushes these mechanisms back to their former positions to end the cycle. The shank or spindle 24 in FIG. 2 is connected to the collet holder 44 in such a way that the collet holder can be rotated on the shank by means of bearings 46 which are held in between the collet holder and shank in the recess 48. The collet holder 44 is rotated by means of a pulley 50 which is connected to the motor 52 by means of V-belt 54. The pulley is splined to the collet holder at 56 so that the collet holder can be rotated by the pulley system, while at the same time it can be reciprocated back and forth by the motion of the shank or spindle.

The pawl holder assembly 36 (see FIGS. 3-6) having a pawl 38 comprises a pawl holder 58, having a slot or cut-out portion 66, wherein the pawl 38 is held by means of pivot pin 62 which is attached to the sides of the slot. The position of the pawl can be regulated by adjusting the screw 64 contained in the threaded hole 66 which extends through the pawl holder from its bottom to its top at the center of the slotted section. The pawl guide 68, which is held to the pawl holder by means of the pawl guide fastener 70, also aides in keeping the pawl in the desired position. By turning the screw 64, the pawl can be positioned with respect to the ratchet wheel so that it can move the ratchet wheel one, two, three or more notches as desired. By this type of control, the incremental depth of the drill can be varied without having to substitute another ratchet wheel having different notched spacings.

The friction plunger mounting 72 as seen in FIG. 6 has for its purpose the buffering of the extra force which is applied by hand or by the solenoid mechanism. Since it only requires a small amount of force to move the pawl which in turn moves the ratchet wheel by the desired number of notches, any additional force would tend to'break the pawl or the ratchet wheel. The frietion plunger mounting has been devised to prevent this situation from developing. It comprises a spring 74 enclosed in the aperture 76 in the thickened portion 78 of the pawl holder, and the plunger 80 which is threaded at one end, where it extends through one side of the aperture. A nut 82 engages the threads to connect the plunger with the pawl holder. The unthreaded side of the plunger extends through the center of the spring. A flanged postioning tube 84 is connected with the pawl holder in order to allow the pawl holder to slide over said tube, and the unthreaded part of the plunger to slide within said tube. In operation the flanged positioning tube strikes the center portion of the ratchet wheel 88 whereupon the pawl holder continues forward compressing spring 74, and is also slammed against the center of the ratchet wheel 88, thereby buffering most of the excess force of the forward stroke. As the pawl holder moves forward to contact the center of the ratchet wheel, the plunger also slides forward through the positioning tube and thereby positions the pawl holder in its forward thrust so that it strikes the ratchet wheel center with its entire surface area in order to equally distribute the force absorption over the entire area. After the excess force is absorbed, the pawl holder is pushed to the rear by the expansion of the spring. In this way, anyone can easily operate my delicate manual drill assembly without excessive care.

My method and apparatus functions with a rotating drill-stationary object system just as well as with a stationary drill-rotating object system. From the above, it can be seen that holes of very small diameters can be drilled in metals, employing my simple method and very inexpensive apparatus.

Many modifications and variations of my invention is possible without departing from the spirit and substance of the invention as disclosed above, the scope of which is commensurate with the appended claims.

I claim:

1. A drill assembly for drilling small holes, comprising a headstock section and a tailstock section, said tailstock section having slidable spindle, a micrometer associated with said spindle, a collet and drill also connected to said spindle, the improvement which comprises first means attached to said spindle for rapidly stroking said spindle forward and rearward, means attached to said micrometer for automatically moving the drill in a determinable but fixed incremental distance during each stroke, and second means attached to said spindle for activating said means attached to said micrometer.

2. The apparatus of claim 1 wherein the first means attached to said spindle consists of a lever system which is operated manually.

3. The apparatus ofclaim- '1 wherein the first means attached to said spindle consists of a solenoid-spring system which is operated electrically.

4. The apparatus of claim 1 wherein the means attached to the micrometer consists of a ratchet ring with evenly spaced notches.

5. The apparatus of claim 1 wherein the second means attached to the spindlecomprises a pawl, a pawl holder assembly for pivotally supporting the pawl, said pawl holder assembly comprising a pawl holder for adjusting the pawl pivot distance, and which contains a friction plunger mounting for absorbing the excess force of the forward stroke.

6. The apparatus of claim 5 wherein said friction plunger mounting comprises a. spring contained in an aperture'of said pawl holder, a plunger, part of said plunger being connected to said pawl holder, and the other part of which is contained within said spring, and a flanged positioning tube connected to said pawl holder so that upon compression of said spring, said plunger will be forced through said flanged tube, and after the excess force is absorbed then be forced to its normal position by the action of the compressed spring.

7. The apparatus of claim 6 wherein the means attached to the micrometer comprises a ratchet ring having evenly spaced notches for engagement with said pawl.

8. The apparatus of claim 7 wherein said drill is References Cited in the file of this patent UNITED STATES PATENTS 323,892 Wesson Aug. 4, 1885 2,581,258 Karweit Jan. 1, 1952 2,768,539 wollenha'uptnue Oct. 30, 1956 

